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-   -   740: Why do I have a Saab valve on my car? And/or is this why I have no power under boost? (https://forums.turbobricks.com/showthread.php?t=279811)

AdmiralSenn 07-10-2013 03:57 PM


Originally Posted by poulrais (Post 4620931)
Well I once had a similar problem on my 744 once and it turned out to be a disconnected wastegate actuator arm. It would build boost but the turbo was working very hard in order to do so. Do you hear a pretty loud hissing sound while on boost?

I do hear a loud hissing, but I just checked and the wastegate actuator is closing and is not stuck open. I applied pressure from my air compressor and at about 7 psi it starts to open and moves without binding or sticking - even a quick pulse of air above 7 psi and it shoots closed. I cannot move it on my own, which I understand is correct operation.

So, here's where I'm at now. This keeps getting more and more confusing.


1) Every second or third start the car will not idle until warm. Resetting the ECU via battery disconnect or fuse pull causes it to idle perfectly.

2) If the car is driven without resetting the ECU, occasional 'thoomp' sounds come from what sounds like the intake on light throttle application in neutral or on a hard acceleration above ~6000 RPM. No issues other than no boost in between those two extremes. Occasionally after one of these I will get a CEL and code 1-1-3 (incorrect mixture), but most of the time nothing.

3) Boost gauge registers pressure according to whatever I set the MBC to, but there is either no power from the turbo or very little.

Things I've done/checked:
Pre-turbo intake hose is now brand new silicone, no change in performance or symptoms.
Turbo to intercooler hose has no cracks. Intercooler to manifold hose is a solid pipe with a straight coupler on one end and an elbow at the throttle body, also no cracks in any of those.
If there are any leaks remaining in the system they are so slight that I cannot detect them.
Idle valve is working correctly.
TPS is adjusted correctly.
Throttle body is clean.
Wastegate is operating correctly.
Plugs are in good condition with a healthy tan color.

I'm leaning towards an electrical issue of some kind, maybe a sensor or ECU fault but I don't even know where else to look. That or I'm an idiot and somehow missed a huge leak, but I think I'm out of potential leaks to investigate. I just pressure tested it again and still can't hear or feel any leaks. Even a slight application of air from the compressor causes any flexible hoses to immediately inflate and there is no hissing except for the air whooshing past the turbo fins.

I am confused.

AdmiralSenn 07-19-2013 05:29 PM

Slight update.

In addition to the list in the last post, the MAF terminals and connector are now brand new, switching MAFs makes zero difference. Also I pulled the cat and it made no difference so it's back on the car. Exhaust is definitely not plugged or restricted.

The last few days, the popping has seemed to be less severe. Now if I hit boost, right when I should feel the power kick in the car acts like it was suddenly attached to an extra half-ton of weight - abrupt slowdown, bucking and fighting unless I ease off the gas. I smell gassy exhaust fairly frequently although the plugs aren't discolored and I can never track down the source, nor am I seeing black smoke or anything of that nature. FPR is not leaking.

I know this thread is all over the place guys, I'm sorry. The symptoms keep shifting and I obviously have more than one issue. Still no codes on fuel or ignition.

What else could this be? Blocked fuel filter? Bad O2 sensor? Bad ignition coil?

Lord_Athlon 07-19-2013 05:33 PM

Sounds like a boost leak honestly. Huge vac leak.

AdmiralSenn 07-19-2013 05:39 PM


Originally Posted by Lord_Athlon (Post 4636370)
Sounds like a boost leak honestly. Huge vac leak.

I know it does, but I simply cannot find one. I am going to replace the rest of the intake hoses next week just in case, but seriously I can't imagine how I could have any leaks left or why I wouldn't be able to find them with a pressure test.

Plus, wouldn't a huge boost leak mean the vac/boost gauge wouldn't register full pressure?

At this point if I have a leak it's got to be something like a crack in the intake manifold or something.

It's really bizarre since if I keep out of boost the car drives beautifully, like a naturally aspirated 16V Volvo.

doucheNozzle 07-19-2013 05:40 PM

Do you have a compressor? You can make an air fitting.

AdmiralSenn 07-19-2013 05:42 PM

I have made a full pressure test rig complete with adjustable pressure nozzle, still can't find a leak. Went up to 22 psi and can't hear or feel anything but the sound of air whooshing past the turbo blades.

Lord_Athlon 07-19-2013 05:46 PM


Originally Posted by AdmiralSenn (Post 4636372)
I know it does, but I simply cannot find one. I am going to replace the rest of the intake hoses next week just in case, but seriously I can't imagine how I could have any leaks left or why I wouldn't be able to find them with a pressure test.

Plus, wouldn't a huge boost leak mean the vac/boost gauge wouldn't register full pressure?

At this point if I have a leak it's got to be something like a crack in the intake manifold or something.

It's really bizarre since if I keep out of boost the car drives beautifully, like a naturally aspirated 16V Volvo.

No it wouldnt. There is a wastegate. Its purpose in simple terms is to maintain pressure in the intake. If the crappy hose coming off the turbo is leaking Xcfm equal to lets say 2-3psi, the wastegate would remain closed and the pressure would stay the same.

AdmiralSenn 07-21-2013 05:55 PM

Well, today I learned something. Thanks! That's the kind of 'duh' stuff I'm missing from just not being terribly well educated about how turbo cars work when taken as a system.

I did pull the compression side air hose off the turbo and check it again today. It's not in great shape but I still can't find any holes through it. A few cracks but none that penetrate through all the way or even much beyond the outer surface. There is a mushy spot near the exhaust manifold but it's still intact. I trimmed the cracked area off but it made no difference.

I'll see what happens when I replace that hose assembly - gotta wait for some income first. The car sounds like a weedwhacker at the moment. I really hope that's it, this is getting ridiculous.

AdmiralSenn 08-12-2013 07:41 PM

Rargh zombie thread.

First of all, I was wrong, you were all right, the CBV was sucking in unmetered air. I don't know how I didn't see it before, maybe it was stuck or something, but yeah that was definitely part of the issue. Pops and stumbling are gone as far as I can tell.

New piping installed, everything from the compressor to the intercooler inlet is new. Pressure test post intercooler holds pressure, pressure test pre compressor leaks down quickly and there is a loud whoosh, but it's not coming from the boost plumbing. The wastegate isn't moving unless I put the air system directly on the line heading to it.

The thing is I can't figure out where the air might be going. Pretty sure the wastegate actuator isn't leaking internally or it wouldn't work when air is applied to it, right?. The air outlet and inlet on the turbo are all brand new silicone and aluminum and it's all tightened down nicely using new T-bolt clamps finished off with a low-power hit from the impact electric wrench just to make sure. The air seems to be coming out near the wastegate actuator or at least on that side, but I'll have to go back to it tomorrow because the manifold was too hot for me to get in there and feel around.

Any ideas, guys? I really can't afford to just yank the turbo out and explore without a REALLY good reason.


Bensin 08-13-2013 06:32 PM

Stock BOV flow directions

Originally Posted by AdmiralSenn (Post 4595910)
Unfortunately there was also a loud POP, which it turns out is from a Bosch valve, item # 0280142105. This seems to be a Saab overpressure valve, which seems to have taken the place of the external CBV that the T3 in the car came with. It was venting to atmosphere, so I guess it's sort of a BOV given the way it's plumbed.

In fact, the more I look at it the more I wonder if it was even hooked up to the correct port at all. The car has always had a strange noise off boost that sounded like really quiet compressor surge, but the previous owner said that it wasn't when I test drove it. This thing has some sort of vacuum diaphragm but pressure from that side wouldn't open up the valve at all as far as I can tell.

Is this a common modification? <strike>I don't remember ever seeing a reference to this being used on a Volvo before.</strike> It looks like I have an oddly numbered variant, I just found a bunch of threads describing very similar parts with final digits off by one or two. Can anyone who's used one of these tell/show me how it should be plumbed?

I'm looking back on your thread, did the BOV get figured out, as mentioned above? If the blow off valve isn't configured right, it certainly could be causing problems.

See this post: http://forums.turbobricks.com/showpo...7&postcount=38 Is this what you have?

Then this image shows how air flows through a stock system. However, the BOV is different than the Bosch. and NOT SHOWN: The vacuum hose running from manifold to BOV.


AdmiralSenn 08-13-2013 08:35 PM

I did get it figured out - it's actually a CBV that was routed as a BOV. As of a few days ago it is correctly installed and the bulk of my driveability and idle problems are gone - still no boost though. And yes, that first link is what I have. My issue was that the vent back into the intake was missing, causing a massive vacuum leak at low/no throttle - the signal line was working fine.

Tomorrow I will be getting the last piece of my new intake put on and then I can test it in earnest - I broke a connector and had to cobble together something using a PVC pipe fitting to make it match up, which has of course already started to deform. (Don't judge me, you can't get anything in this town!) My custom aluminum replacement should be done tomorrow.

So as of now it's basically running like a B234F.

AdmiralSenn 08-17-2013 05:48 PM

Okay, a few days driving around with the completed intake. I now get intermittent moments of boost, although it seems to depend a lot on how warm things are.

I have to put the car up to change the oil shortly and will be taking off the belly pan so I can inspect the turbo more closely. The last air leak I can hear is coming from inboard on the turbo, near the wastegate. I'm starting to think that something is cracked.

Any ideas on what to look for besides an obvious hole?

AdmiralSenn 09-23-2013 06:37 PM

Nope, this thread still isn't dead yet. Miraculously, the car isn't either.

I finally have some time to work on the stupid car again. I've been driving it around and it seems to have settled into a reliable, if slow and boring, mode of operation. Pathetic attempts at boost when cold, getting less punchy as it warms up. Otherwise runs rock solid.

After buying a few more pieces for my kit, I have conclusively determined that the leak is either in the turbo housing itself or the wastegate actuator. I am leaning towards the actuator but before I go buying parts I want to check that I'm not crazy.

(Just for reference, the way I determined this was by applying a pressure plug to the turbo outlet and pressurizing the intake as normal. Pressure will not build in this configuration unless I hold the air compressor valve open. I did a similar test to rule out the intercooler with a perfect result - it held pressure north of 20 psi.) I can hear air leaking somewhere but I cannot feel air leaking anywhere.

Previously if I tested the wastegate actuator by applying air pressure directly to the signal hose, it would instantly move. However, if I pressurize the turbo from the air inlet, it doesn't start to move until around 30-40 psi! This strikes me as being a big problem. If I happen to be wrong here please let me know, but I think I'm finally on to something given that it's supposed to open at 7-8 psi stock.

If it ever stops raining (not going to risk my life on jackstands on a sloped, wet driveway), I am going to pull the actuator out, check the wastegate arm for smooth operation, and check for a blown gasket. Assuming I find a smoking gun in there, any recommendations for a Garrett T3 wastegate actuator? I don't mind spending a bit extra for something I can use for years. Current plans are to keep the car at ~12 psi until I can swap the M46 for something less likely to explode, so something adjustable would be nice but not necessary right away. I keep seeing references to a Forge unit but their website doesn't have one specifically for the T3, so it's probably a crossover and I have no idea which variant would be the right one - advice would be awesome!

Thanks again guys. With any luck I can FINALLY put this stupid project to rest and focus on something more fun.

AdmiralSenn 09-27-2013 08:29 PM

Help! Wastegate actuator
Okay, I ordered an ipd wastegate actuator and it's here and I'm trying to install it. The rod is a lot longer than the one that was on the car. Like, 1.5 - 2 inches longer.

Barring the rod difference, they look exactly the same. I believe the old one is the original T3 actuator. The old rod was not cut, it still has the original machined end.

Am I going to run into trouble here? It looks like it's enough of a difference that the wastegate will be stuck fully open at all times. But I don't want to be stupid and trim down the rod and end up in a runaway boost situation either.

Anyone run into anything like this before?

(By the way the old one was definitely leaking internally, although I don't yet know if this will fix the problem or not.)

AdmiralSenn 10-01-2013 12:01 AM

(Is anyone even still reading this? I know I'm rambling all over the place here.)

Ended up trimming the female-threaded portion of the actuator rod to fit, seems to work okay. I have no idea why they are different, the ipd one matches the ones I've seen in pictures for a T3. Once again my car is just weird. I'm wondering if maybe the previous owner threw a misfit Saab actuator on there at some point or something.

The new actuator was either the last air leak or at least the last major one, although I believe I have just traded an air quantity/pressure problem for a combustion problem since I'm not back to 100% operation yet.

When cold, the car will almost always take off like a rocket, just like when I first got it or near enough as makes no difference. As it warms up, it gets less punchy, until when it's fully warmed up it does something really odd.

Basically if I stomp on it, it will rev, build boost, nothing will happen, then I will get a backfire/pop (same noise as before, hollow sounding, more of a 'FOOMP' than anything else) accompanied by a fluttery/surgy noise, then at the upper end of the powerband it will suddenly catch and start moving, but by that point I've already let off the gas due to fear of damage. (I have stopped hitting the pedal hard because I believe I will cause some pricey, exciting damage if I keep trying it that way). It's actually kind of similar to the sensation of a turbo hose popped loose, only self-correcting.

If I had to describe it to a non-Volvo person I would say that it almost feels like it's building pressure against an obstruction, then blowing the obstruction loose at around 4-5000 RPM and resuming normal operation. I know that doesn't make much sense but that's the best way I can describe it.

If I feather the throttle carefully, it will accelerate fine, and sometimes even get a little bit of boost.

At this point I'm thinking I just need to start doing the rest of the stage 0 stuff, plugs/wires/cap/rotor, fuel filter, and see if that helps. RPM sensor is new, AMM is supposedly from a known good car although I may pick up a few more to see what happens.

Anyone have any 'check this first' stuff? My budget at the moment is less fantastic than usual, so I can't really afford to shotgun replace parts at this point.

AdmiralSenn 10-11-2013 05:54 PM

Update, fuel filter and plugs replaced.

Old fuel filter dripped brownish gas out, which left a nice debris residue after it evaporated. "Well, there's your problem..." Immediately the car ran smoother, but still no power.

Checked the plugs, and DANG my plugs got nasty FAST. In July I checked them and they seemed fine, the other day I decided to replace them just for kicks and giggles and three of them showed the charcoal-ish buildup of really nasty fuel deposits and such. Replaced with NGK BPR6ES @ .030" and the bulk of my problems seems to have gone away. I now have boost most of the time even when hot, although about half of the time it will still act like I have a huge boost leak. It seems to be getting better over time, and I'm guessing that the clean fuel is slowly cleaning the injectors out.

I will most likely eventually replace the injectors if I find a good new or rebuilt set of brown tops or equivalent that I can afford. May toss in some concentrated injector cleaner or something and see what happens.

Thanks for all the help, guys. I think I can call this issue closed and I am now moving on to the next problem, which is a big backlog of cosmetic issues and a state of general disassembly I need to address.

Yay for boost!

doucheNozzle 10-13-2013 09:39 PM


AdmiralSenn 10-13-2013 09:55 PM

Indeed! I am quite pleased. I've even had a few runs where it approached or met the original performance when I bought the car. I think I'm going to dial the wastegate back in a turn or two and use the MBC to adjust boost from here on out though.

Bensin 10-14-2013 01:31 PM

Only sparkplugs - that's cool!

AdmiralSenn 10-14-2013 04:47 PM

Well, spark plugs, fuel filter, wastegate actuator, boost pipes and intake hose, and a poorly plumbed external CBV. Everything contributed and although it's still not 100%, it's getting there.

Now I just need to figure out why there's such a dramatic difference between when it's hot and when it's cold.

doucheNozzle 10-15-2013 02:05 PM


Originally Posted by AdmiralSenn (Post 4713738)
Well, spark plugs, fuel filter, wastegate actuator, boost pipes and intake hose, and a poorly plumbed external CBV. Everything contributed and although it's still not 100%, it's getting there.

Now I just need to figure out why there's such a dramatic difference between when it's hot and when it's cold.

CTS could be bad.

Janspeed 10-15-2013 06:05 PM

that could also cause plug fouling. if coolant temp sensor is broken it may be getting over-rich mixture.

about the WGA: it should have some preload (like half the pin visible through the rod hole while the rod is detached)
dail in the desired boostlevel by using the boostcontroler. You should start to feel the boost from about 2200 on up. From 3000 on up the car should be hauling ass.

as for boostleaks: make sure the manifold has no leaking exhaust gaskets. And the turbo should be tightened down to avoid leaks between manifold and turbine. The compressor housing has a rubber seal or gasket between backingplate and snailhousing. If that leaks you also lose boost.
It's all in the details.

AdmiralSenn 10-15-2013 08:08 PM

I'll check the resistance on the CT sensor this week and see what happens. I do have a fancy Volvo OEM replacement on the shelf just in case, but I don't have an intake manifold gasket handy, will have to acquire one before I try to replace it.

Wastegate actuator is defintiely slightly too preloaded, this is on my list of things to deal with. I picked up an extra 3 pounds of boost. Just haven't had enough time between drives for the motor to cool off, and this weekend I was fighting a sinus thing and didn't even leave the house. When it picks up power it's pretty early, when it gets hot and stops boosting I don't feel the initial power onset until ~3500-4000.

Fairly sure the exhaust side isn't leaking, I haven't seen or heard any symptoms of an exhaust leak. I will check the turbo mounting studs on the manifold though.

I will have to do another intake leak test and make sure there isn't any air going anywhere it shouldn't. If there is one it's likely going to be in the turbo itself, probably the seal you describe. If that's the case I'll just have to live with the reduced performance until I can afford a replacement - I'm not going to risk the downtime on the car to rebuild the turbo if I can swap in a known good replacement and get more power out of it at the same time. Not sure what my options are for a water cooled T3 or T3/T4 that I could ever afford, though.

I'll update when I find something.

doucheNozzle 10-16-2013 10:10 AM

Do you have EGR on the car?

AdmiralSenn 10-16-2013 09:03 PM

Nope, no EGR.

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